Investigation on activation characterization, secondary electron yield, and surface resistance of novel quinary alloy Ti-Zr-V-Hf-Cu non-evaporable getters.

The performance of next-generation particle accelerators has been adversely affected by the occurrence of electron multipacting and vacuum instabilities. Particularly, minimization of secondary electron emission (SEE) and reduction of surface resistance are two critical issues to prevent some of the phenomena such as beam instability, reduction of beam lifetime, and residual gas ionization, all of which occur as a result of these adverse effects in next-generation particle accelerators. For the first time, novel quinary alloy Ti-Zr-V-Hf-Cu non-evaporable getter (NEG) films were prepared on stainless steel substrates by using the direct current magnetron sputtering technique to reduce surface resistance and SEE yield with an efficient pumping performance. Based on the experimental findings, the surface resistance of the quinary Ti-Zr-V-Hf-Cu NEG films was established to be 6.6 × 10-7 Ω m for sample no. 1, 6.4 × 10-7 Ω m for sample no. 2, and 6.2 × 10-7 Ω m for sample no. 3. The δmax measurements recorded for Ti-Zr-V-Hf-Cu NEG films are 1.33 for sample no. 1, 1.34 for sample no. 2, and 1.35 for sample no. 3. Upon heating the Ti-Zr-V-Hf-Cu NEG film to 150 °C, the XPS spectra results indicated that there are significant changes in the chemical states of its constituent metals, Ti, Zr, V, Hf, and Cu, and these chemical state changes continued with heating at 180 °C. This implies that upon heating at 150 °C, the Ti-Zr-V-Hf-Cu NEG film becomes activated, showing that novel quinary NEG films can be effectively employed as getter pumps for generating ultra-high vacuum conditions.

Activation characterization of a novel quinary alloy Ti-Zr-V-Hf-Nb non-evaporable getters by x-ray photoelectron spectroscopy.

The first results on the activation process and mechanisms of novel quinary alloy Ti-Zr-V-Hf-Nb non-evaporable getter (NEG) film coatings with copper substrates were presented. About 1.075 µm of Ti-Zr-V-Hf-Nb NEG film coating was deposited on the copper substrates by using the DC sputtering method. The NEG activation at 100, 150, and 180 °C, respectively, for 2 h was in situ characterized by x-ray photoelectron spectroscopy (XPS). The as-deposited NEG film mainly comprised the high valence state metallic oxides and the sub-oxides, as well as a small number of metals. The in situ XPS studies indicated that the concentrations of the high-oxidized states of Ti, Zr, V, Hf, and Nb gradually decreased and that of the lower valence metallic oxides and metallic states increased in steps, when the activation temperature increased from 100 to 180 °C. This outcome manifested that these novel quinary alloy Ti-Zr-V-Hf-Nb NEG film coatings could be activated and used for producing ultra-high vacuum.